// echo_server.cc
#include <fcntl.h> // fcntl
#include <stdlib.h> // exit
#include <sys/select.h> // select
#include <sys/socket.h> // socket
#include <netinet/in.h> // sockaddr_in
#include <strings.h> // bzero
#include <arpa/inet.h> // inet_addr
#include <errno.h> // errno
#include <unistd.h> // read
#include <stdio.h> // perror
#include <string.h> // memset
#include <iostream>
int main()
{
std::cout << "start select echo server..." << std::endl;
static const int max_back_log = 10;
int cur_conn_nun = 0;
int fd_conn_arr[max_back_log];
int listenfd = socket(AF_INET,SOCK_STREAM,0);
if(-1 == listenfd)
{
std::cout << "error at socket" << std::endl;
exit(1);
}
int option_name = 1;
if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &option_name, sizeof(int)) == -1)
{
perror("setsockopt");
exit(1);
}
struct sockaddr_in serveraddr;
bzero(&serveraddr,sizeof(sockaddr_in));
serveraddr.sin_family = AF_INET;
serveraddr.sin_port = htons(9877);
inet_aton("127.0.0.1",&(serveraddr.sin_addr));
bind(listenfd,(sockaddr*)&serveraddr,sizeof(sockaddr_in));
listen(listenfd,max_back_log);
fd_set fd_flag;
int connectfd = 0;
struct sockaddr_in clientaddr;
struct timeval tv;
socklen_t client_addr_len;
int read_size = 0;
int send_size = 0;
int read_data = 0;
int fd_max = listenfd;
memset(fd_conn_arr,0,sizeof(int)*max_back_log);
while(1)
{
FD_ZERO(&fd_flag);
FD_SET(listenfd,&fd_flag);
tv.tv_sec = 15;
tv.tv_usec = 0;
for(int i = 0; i < max_back_log; ++i)
{
if(fd_conn_arr[i] != 0)
{
FD_SET(fd_conn_arr[i],&fd_flag);
}
}
int ret = select(fd_max + 1,&fd_flag,NULL,NULL,&tv);
if(-1 > ret)
{
perror("error at select");
exit(1);
}
else if(0 == ret)
{
perror("select time out");
continue;
}
for(int i = 0; i < cur_conn_nun; ++i)
{
if(FD_ISSET(fd_conn_arr[i],&fd_flag))
{
if((read_size = read(fd_conn_arr[i],(void*)&read_data,sizeof(int))) < 0 )
{
std::cout << "read error" <<std::endl;
}
else
{
std::cout << read_size << " bytes data read: " << read_data << std::endl;
}
if((send_size = write(fd_conn_arr[i],(void*)&read_data,sizeof(int))) < 0 )
{
std::cout << "read error" <<std::endl;
}
else
{
std::cout << send_size << " bytes data send: " << read_data << std::endl;
}
}
}
if(FD_ISSET(listenfd,&fd_flag))
{
connectfd = accept(listenfd,(sockaddr*)&clientaddr,&client_addr_len);
if(-1 == connectfd)
{
perror("error at accept");
continue;
}
if(cur_conn_nun < max_back_log)
{
fd_conn_arr[cur_conn_nun++] = connectfd;
if(fd_max < connectfd)
{
fd_max = connectfd;
}
}
std::cout << "new connection coming at " << inet_ntoa(clientaddr.sin_addr) << ": " << ntohs(clientaddr.sin_port) << std::endl;
}
}
return 0;
}
// echo_client
#include <stdlib.h> // exit
#include <netinet/in.h> // sockaddr_in
#include <strings.h> // bzero
#include <arpa/inet.h> // inet_addr
#include <sys/socket.h>
#include <iostream>
int main()
{
int sock = socket(AF_INET,SOCK_STREAM,0);
if(-1 == sock)
{
std::cout << "error at socket"<<std::endl;
exit(1);
}
struct sockaddr_in clientaddr;
clientaddr.sin_family = AF_INET;
clientaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
clientaddr.sin_port = htons(9877);
int res = connect(sock,(sockaddr*)&clientaddr,sizeof(sockaddr_in));
if(-1 == res)
{
std::cout << "error at connect"<<std::endl;
exit(1);
}
static int send_data = 1;
for(;;)
{
int send_bytes = send(sock,(void*)&send_data,sizeof(int),0);
if(-1 != send_bytes)
{
std::cout << send_bytes << " bytes data send: " << send_data++ << std::endl;
}
int recv_data = 0;
int recv_bytes = recv(sock,(void*)&recv_data,sizeof(int),0);
if(-1 != recv_bytes)
{
std::cout << recv_bytes << " bytes data recv: " << recv_data << std::endl;
}
sleep(1);
}
}
與WINDOWS版本不同的是 select 的第一個參數
nfds
linux 版本
The nfds argument specifies the range of descriptors to be tested. The firstnfds descriptors shall be checked in each set; that is, the descriptors from zero throughnfds-1 in the descriptor sets shall be examined.
windows 版本
nfdsIgnored. The nfds parameter is included only for compatibility with Berkeley sockets.
其次遇到的問題是 Address already in use,使用 if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &option_name, sizeof(int)) == -1) 解決。